Automatic leveling system



p 1967 G'. w. JACKSON AUTOMATIC LEVELING SYSTEM Original Filed Nov. 30,1964 2 Sheets-Sheet l INVENTOR. George W Jackson BY H/s Af/omey Sept. 5,1967 G. W. JACKSQN AUTOMATIC LEVEL ING SYSTEM 2 Sheets-Sheet? OriginalFile d Nov. 30, 1964 INVENTOR. George WJac/rson His A/forney directingUnited States Patent 3,339,910 AUTOMATIC LEVELING SYSTEM George W.Jackson, Dayton, Ohio, assignor to General Motors Corporation, Detroit,Mich., a corporation of Delaware Continuation of application Ser. No.414,740, Nov. 30, 1964. This application Aug. 22, 1966, Ser. No. 574,2549 Claims. (Cl. 267-65) This application is a continuation of Ser. No.414,740, filed on Nov. 30, 1964, now abandoned.

This invention relates to systems for automatically maintaining apredetermined height relationship between a sprung and an unsprung massand, more particularly, to such systems that include a combination shockabsorber and an air booster spring pressurizable by a suitable fluidaffects the general riding qualities of the vehicle.

An object of the present invention, therefore, is to automaticallymaintain a desired height relationship be tween the sprung body and theunsprung frame axle wheel assembly of a vehicle by means of acombination shock absorber and air spring unit having an improved closedfluid system associated therewith for selectively pressurized fluid toand from the air spring in response to changes in the weight of thesprung mass for causing the shock absorber unit in combination with aprimary spring suspension system to maintain the sprung mass at adesired predetermined height relationship with the unsprung mass.

A further object of the present invention is to automatically maintain adesired height relationship between a sprung and an unsprung mass by theprovision of a combination shock absorber and air spring unit adapted tobe located between the sprung and unsprung mass for damping the roadinduced relative movements therebetween wherein the air spring isassociated with an improved closed fluid pressure system including ahermetically sealed compressor and fluid control valve selectivelyoperable by means responsive to changes in the weight of the sprung massto cause the air spring to be selec tively inflated and deflated tomaintain the desired height relationship.

A still further object of the present invention is to automaticallymaintain a desired height relationship between a sprung and an unsprungmass by the provision of a combination shock absorber and air springunit and a I closed fluid system for supplying pressurized fluid to andfrom the air spring including an electric motor driven compressor forpressurizing fluid and an electrically energizable solenoid valve forcontrolling fluid flow and switch means for selectively connecting thecompressor motor solenoid valve to a source of power in response tochanges in'the weight of the sprung mass; and to provide such a systemwherein the compressor and solenoid valve are included in a hermeticallysealed tank con- I stituting a portion of the closed fluid system.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

In the drawings:

FIGURE 1 is a schematic view of an automatic leveling system includingthe present invention;

FIGURE 2 is an enlarged, fragmentary, sectional view of an electricalswitch actuator in FIGURE 1;

FIGURE 3 is a schematic view of a modification of the system of FIGURE1; and

FIGURE 4 is a diagrammatic view of an electrical circuit for controllingthe operation of the system shown in FIGURE 1.

Referring now to the drawings, in FIGURE 1, an improved automaticleveling system 10 is illustrated including a pair of combination shockabsorber and air spring units 12, 14. Each of the units are of the typemore particularly set forth in United States Patent No. 3,063,701,issued Nov. 13, 1962, to Paul J. Long, Jr., for Shock Absorber With AirBooster Spring.

As explained more fully in the Long patent, such units are connectedbetween the sprung and unsprung masses of a vehicle for damping therelative movements between the sprung and unsprung masses produced bynormal road movements and for supplementing the load carrying action ofa primary suspension system between the sprung and unsprung masses tomaintain a desired height relationship therebetween.

For example, automobile bodies are preferably maintained at apredetermined design height at all times whether the car is unloaded orfully loaded. At such a headlights are accurately aimed on the road andthe sprung mass is sufficiently elevated to prevent bottoming againstframe stops or scraping thereof on steep inclines. Additionally, at sucha design height steering control is more responsive and positive.

For purposes of understanding the present invention, it should bepointed out that each of the combination units 12, 14 includes a shockabsorber unit 16 having a cylindrical outer surface 18 closed by an endclosure member 20 at one end thereof and by an end closure member 22 atthe opposite end thereof. On the closure member 20 is secured a bearingmount 24 adapted to be connected to the unsprung mass of a vehicle andat the opposite end of the shock absorber 16 a reciprocal piston rod 26is directed through the end cap 22 exteriorly thereof where its outerend is secured to an upper bearing mount 28 adapted to be secured to thesprung mass.

Carried on the reciprocal piston rod 26 is a tubular, rigid, elongatedmember 30 having an upper open end 7 thereof closed by a top wall 32that is fixed to the piston rod 2-6 for movement therewith by fitting ina reduced diameter portion 34 of the rod. The member 30 is arrangedconcentrically of the outer cylindrical surface 18 of shock absorberunit 16 in spaced telescoping relationship therewith wherein a space 35is formed between it and the outer surface 18. The opposite opened endof the member 30 is closed by a flexible sleeve 36 of resilient materialhaving one end 37 thereof surrounding the open end of the member 30 incontinuous engagement therewith and being fastened into a sealingrelationship thereon by a clamp ring 38. The sleeve '36 is rolledinwardly of end 37 to form a return bend portion 40 that connects theend 37 to an inwardly located tubular sleeve extension 36, member 30 andshock absorber 16 thereby in combination close the space 35 againstfluid leakage exteriorly thereof. In the illustrated arrangement thetubular mem- 3 ber 30 of unit 14 has a fluid inlet fitting 46 directedtherethrough and an outlet fitting 48 for directing fluid from the space35 exteriorly of the combination unit. The system also includes aconduit 49 connected to each of the units 12, 14 for intercommunicatingthe spaces 35 therein.

The fluid fittings 46, 48 are in communication with a closed pressuresystem 50 that is schematically illustrated as including an electricalmotor driven compressor 52 supported within a pressure enclosure orshell 54 by a plurality of mounting springs 56, 58, 60 representativelyillustrated as being tension springs having the opposite ends thereofsecured to spaced points on the inner surface of the enclosure 54 andthe outer shell of the compressor 52. The enclosure 54 hermeticallyseals the compressor 52 and in the embodiment of the inventionillustrated in FIGURE 1, the compressor 52 is shown to have an inlet 51and an outlet 53 thereof connected to a conduit 62 directed through asealing grommet 64 in the shell 54 exteriorly thereof where it isconnected to the inlet fitting 46.

The system further includes a conduit 65 connected to the outlet fitting48 and to a solenoid actuated exhaust valve assembly 66 supportedinteriorly of the shell 54 and including an outlet 70 for directing airexhausted from the pressurizable spaces 35 into the shell 54.

The shell 54 serves as a low-pressure reservoir in the closed system ofFIGURE 1 for hermetically sealing the compressor 52 from dirt, moistureand the like in the surrounding atmosphere. Addition-ally, the shellserves as a means for isolating the noise of compressor operation.

The compressor 52 is driven by an electrical drive motor 72 associatedtherewith and the exhaust valve 66 includes an electricall energizablesolenoid coil 74 shown in FIGURE 4 in an electrical control circuit 76that is connected to a power source, for example, a battery 78 by aheight control switch 80, that is carried on the tubular member 30 ofthe superlift unit. The switch 80 is a single-pole, double-throw switchhaving a movable contact carrying member 82 which is selectivelypositioned by a movable actuator means 84 associated with the sprungmass. The member 82 is positioned by relative movement between thesprung and the unsprung masses to selectively engage a fixed contact 86to complete a motor energization circuit 88 or a fixed contact 89 tocomplete a solenoid coil energization circuit 90.

In the structural views of FIGURES 1 and 2 the switch 80 is shown ashaving an outer housing 92 thereof secured to the outside of tubularmember 30 where a screw 94 directed outwardly of housing 92 into space'35 is fastened to the actuator means 84 at one end thereof and has ahead 95 thereon biased by a spring 96 against shock absorber 16.Movement of member 30 causes reciprocation of screw 94 which is thenrotated upon engaging pins 97 fixed in a rigid part of the switch 80 tothereby cause actuator means 84 to open and close the switch 80.

A representative single-pole, double-throw switch is more specificallyset forth in United States Patent No. 2,921,160, issued J an. 12, 1960,to Lautzenhiser, for Electric Switch. The switch is of the damped typewherein high-frequency road movements do not move the movable member 82.The member is moved into its respective switching positions by changesin the weight of the sprung mass that cause a relative movement betweenthe bearing mounts 24, 28 on the ends of the combination shock absorberand air spring unit.

Thus, in operation, assuming that the sprung and unsprung masses are ata desired height relationship, the movable member 82 is positionedintermediate the contacts 86, 89 whereby the system is deenergized.

Upon an increase in load that causes the primary suspension spring tocompress so that the ends of the shock absorber are moved closertogether from the desired predetermined height relationship, the movableswitch member 82 is eventually moved into engagement with the contact 86for energizing the run winding of the compressor motor 72. Fluid isthereby drawn from the interior of shell 54 and discharged through theinlet fitting 46 into one of the pressurizable chambers 35 thencethrough conduit 49 into the other of the chambers 35 to cause theflexible tubular sleeves 36 to be inflated to produce a supplementalload carrying spring action that will move the sprung and unsprungmasses back to their desired height relationship. When the combinationunits are so orientated, any unloading of the vehicle will, because ofthe pressure in the chambers 35, cause the shock absorbers to extend sothat their ends are separated a distance in excess of the predeterminedheight relationship to cause the movable arm 82 to move out ofengagement with the contact 86 and to move into engagement with thesolenoid actuated exhaust valve contact 89 whereby the solenoid valve 66is conditioned to exhaust fluid from chambers 35 through the conduit 65interiorly of the shell 54.

The movable arm 82 pulsatingly controls both the solenoid exhaust valveand compressor motor to maintain the desired height relationship througha wide range of loading conditions.

In certain cases the sprung mass is overloaded so as to cause thecompressor motor contacts 86 to continually engage the movable contactcarrying arm 82. By virtue of the illustrated arrangement, thecompressor 52 is only able to produce a predetermined maximum pressurein the pressurizable chamber 35 before it draws a vacuum in the inletreceiver formed by the shell 54. Thus, the closed system serves as abuilt-in safety device against overinflation.

Additionally, when the vehicle is normally loaded so that the mainspring system carries the sprung and unsprung masses at a desired heightrelationship, the volume of the system and the amount of compressiblefluid therein is such that the system will be balanced at apredetermined minimum pressure whereby the inflatable sleeve 36 is heldout of engagement with itself so as to limit undesirable wear.

In FIGURE 3 a modified system 100 is illustrated which is like system 10but with an electric motor driven compressor 102 and solenoid valve 104hermetically sealed within a shell 105 that receives pressurized fluidfrom an outlet 106 of compressor 102. The valve 104 serves to directpressurized fluid into combination units 102, 110 like units 12, 14through a conduit 112 and a conduit 114 serves as an exhaust line thatis connected to an inlet 115 of the compressor 102. By virtue of thisarrangement, an instantaneous source of pressure is available in shell105 of maintaining a desired height relationship. When valve 104 isclosed, compressor operation will draw fluid from the pressurizablechambers in the combination units 108, 110 to reduce the pressuretherein upon reducing the weight of a sprung mass partially supportedthereby.

While the embodiment of the present invention as herein dislosedconstitutes a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. In an automatic leveling system for maintaining a predeterminedheight relationship between a sprung and an unsprung mass, thecombination of, a shock absorber unit, fluid spring means supported onsaid shock absorber unit for adjusting the length of said shock absorberunit to maintain the sprung mass at a predetermined height relationshipwith respect to the unsprung mass, a source of pressure for inflatingsaid fluid spring means including a compressor, means including asolenoid valve for controlling the pressure level in said fluid springmeans, a source of power for driving said compressor, switch meansresponsive to changes in said load of the sprung mass for selectivelyoperating said compressor and said solenoid valve to modulate thepressure in said fluid spring means to maintain the desired heightrelationship between the sprung and unsprung masses.

2. In an automatic leveling system for maintaining a predeterminedheight relationship between a sprung and an unsprung mass, thecombination of, fluid spring means including a pressurizable chamber tomaintain the sprung mass at a predetermined height relationship withrespect to the unsprung mass, a source of pressure for inflating saidfluid spring means chamber including a compressor, means forhermetically enclosing said compressor, fluid control means forselectively directly pressurized fluid between between said compressorenclosure means and said fluid spring unit, and means responsive tochanges in the load of the sprung mass to selectively drive saidcompressor for compressing fluid and to condition said fluid controlmeans to direct a predetermined amount of pressurized fluid between saidenclosure means and fluid spring means for maintaining the desiredheight relationship.

3. In the combination of claim 2, said enclosure means serving as alow-pressure reservoir for directing fluid to the inlet of thecompressor, said fluid control means including solenoid valve means forexhausting pressurized from said fluid spring means into said enclosuremeans.

4. In the combination of claim 2, said compressor having its outletcommunicating with said enclosure means, said enclosure means serving asa prepressurized source of fluid for inflating said fluid spring means,said fluid control means including solenoid actuated valve meansenergizable to direct pressurized fluid from said enclosure means to thefluid spring means, said compressor having an inlet directlycommunicating with said fluid spring means whereby energization of thecompressor causes the compressor to draw fluid from said fluid springmeans and discharge it into said enclosure means from whence it isdirected under control of said valve means. 5. In an automatic levelingsystem for maintaining a predetermined height relationship between asprung and an unsprung mass, the combination of, a shock absorber havingthe ends thereof adapted to be connected to the sprung and unsprungmasses respectively, fluid spring means supported by said shock absorberfor maintaining a predetermined distance between the ends thereof tomaintain the desired height relationship, means for pressun'zing saidfluid spring means including an electric compressor drive motor, asource of power, height control switch means supported on said shockabsorber including means actuatable upon a predetermined relativemovement between the sprung and unsprung masses for selectivelyconnecting the compressor motor to the source of power for effecting apredetermined pressurization of said air spring means, saidpressurization means including a solenoid valve for controlling thepressure level in said fluid spring means, said height control switchsensing the load of the sprung mass for selectively operating saidcompressor motor and said solenoid valve to modulate the pressure insaid fluid spring means to maintain the desired height relationship.

6. In an automatic leveling system for maintaining a predeterminedheight relationship between a sprung and an unsprung mass, thecombination of, a shock absorber having the ends thereof adapted to beconnected to the sprung and unsprung masses, a fluid spring unitsupported by said shock absorber including an expansible pressurizablechamber for moving the ends of the shock absorber relative to oneanother to maintain a predetermined desired height relationship betweenthe sprung and unsprung masses, a motor driven compressor, an enclosurefor hermetically sealing the compressor, means for resilientlysupporting the compressor within the sealed enclosure, means fordirecting pressurized fluid from the compressor into the expansiblepressurizable chamber of said air spring unit, a source of power, aheight control electrical switch means, coacting means on said shockabsorber and fluid spring unit for conditioning said switch means upon afirst predetermined height relationship between said sprung and unsprungmasses for connecting the compressor drive motor to the source of power,exhaust valve means for deflating said fluid spring unit, and saidcoacting means conditioning said height control switch on a secondpredetermined height relationship between the sprung and unsprung massesto de-energize the compressor motor and energize the exhaust valve meansso as to maintain the desired predetermined height relationship.

7. In an automatic leveling system for maintaining a predeterminedheight relationship between a sprung and an unsprung mass, thecombination of, a shock absorber having the ends thereof adapted to beconnected to the sprung and unsprung masses, fluid spring meanssupported by said shock absorber including an expansible pressurizablechamber for moving the ends of the shock absorber relative to oneanother to maintain the predetermined desired height relationshipbetween the sprung and unsprung masses, a source of pressure including amotor driven compressor, an enclosure :for hermetically sealing saidcompressor, fluid control means for selectively directing pressurizedfluid between said compressor enclosure and the expansible pressurizablechamber of said fluid spring means, a source of power, a height controlelectrical switch means, coacting means on said shock absorberand fluidspring means for conditioning said switch means upon a firstpredetermined height relationship between said sprung and unsprungmasses for connecting said motor driven compressor to the source ofpower, said coacting means conditioning said height control switch upona second predetermined height relationship between the sprung andunsprung masses to deenergize said motor driven compressor and conditionsaid fluid control means to deflate said fluid spring means so as tomaintain the desired predetermined height relationship.

8. In the combination of claim 7, said enclosure serving as thelow-pressure reservoir for directing fluid to the inlet of thecompressor, said fluid control means including solenoid valve means forexhausting pressurized fluid from said fluid spring means into saidenclosure.

9. In the combination of claim 7, said compressor having its outletcommunicating with the interior of said enclosure, said enclosureserving as a prepressurized source of fluid for inflating said fluidspring means, said fluid control means including solenoid actuated valvemeans energizable to direct pressurized fluid from said enclosure tosaid fluid spring means, conduit means for communicating said fluidspring means directly with the inlet of said compressor wherebyenergization of the compressor causes the compressor to draw fluid fromsaid fluid spring means and discharge it into said enclosure.

References Cited UNITED STATES PATENTS 2,536,626 1/1951 Coleman 267-643,026,103 3/1962 Gates 267-65 3,120,962 2/1964 Long 267-64 3,173,6713/1965 Broodwell 267-64 ARTHUR L. LA POINT, Primary Examiner.

R. M, WOHLFARTH, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,339,910 September 5, 1967 George W. Jackson It is hereby certifiedthat error appears in the above numbered patent requiring correction andthat the said Letters Patent should read as corrected below.

In the heading to the printed specification, line 6 and column 1, line10, for '414,74O", each occurrence, read 4l4,746 line 18, for "system"read systems column 4, line 47, for "102" read 108 line 51, for "of"read for line 73, for "said" read the column 5, line 11, for "directly"read directing Signed and sealed this 12th day of November 1968.

(SEAL) Attest:

Edward M. Fletcher, Jr. EDWARD J. BRENNER Attesting Officer Commissionerof Patents

1. IN AN AUTOMATIC LEVELING SYSTEM FOR MAINTAINING A PREDETERMINEDHEIGHT RELATIONSHIP BETWEEN A SPRUNG AND AN UNSPRUNG MASS, THECOMBINATION OF, A SHOCK ABSORBER UNIT, FLUID SPRING MEANS SUPPORTED ONSAID SHOCK ABSORBER UNIT FOR ADJUSTING THE LENGTH OF SAID SHOCK ABSORBERUNIT TO MAINTAIN THE SPRUNG MASS AT A PREDETERMINED HEIGHT RELATIONSHIPWITH RESPECT TO THE UNSPRUNG MASS, A SOURCE OF PRESSURE FOR INFLATINGSAID FLUID SPRING MEANS INCLUDING A COMPRESSOR, MEANS INCLUDING ASOLENOID VALVE FOR CONTROLLING THE PRESSURE LEVEL IN SAID FLUID SPRINGMEANS, A SOURCE OF POWER FOR DRIVING SAID COMPRESSOR, SWITCH MEANSRESPONDSIVE TO CHANGES IN SAID LOAD OF THE SPRUNG MASS FOR SELECTIVELYOPERATING SAID COMPRESSOR AND SAID SOLENOID VALVE TO MODULATE THEPRESSURE IN SAID FLUID SPRING MEANS TO MAINTAIN THE DESIRED HEIGHTRELATIONSHIP BETWEEN THE SPRUNG AND UNSPRUNG MASSES.